Olivia Judson: How To Stage a Resurrection

ONCE MORE we have the pleasure of reading a new column by the splendidly-evolved Olivia Judson. She is an evolutionary biologist and a research fellow in biology at Imperial College London.

This article, part of Dr. Judson’s series in the New York Times, is titled Resurrection Science, in which Olivia writes about the science of re-creating an extinct species, like the mammoth. Here are some excerpts, with bold added by us:

The outline of how to stage a resurrection is clear. In essence, it’s a matter of cross-species cloning — using an egg from one species to host the genome of the other. The procedure is more or less the same as for regular cloning. First, you make a “blank” egg by removing the egg’s nucleus — this contains the egg’s genome. You then insert the genome of the animal you want to clone.

But then Olivia informs us that cloning is far from a reliable process:

In the decade since Dolly the Sheep was cloned, enormous progress has been made on regular cloning. To date, more than 10 different species of mammal have been cloned, including ferrets, rabbits, horses, cows and pigs. Nonetheless, success rates are still extremely low. Even for cows, the animals that have been cloned the most, fewer than 5 percent of embryos transferred to surrogate mothers result in offspring. A recent report on dog clones illustrates the problem: of 358 embryos transplanted into 20 females, two pregnancies became established, and only one puppy was born.

However …

Given the difficulties of normal cloning, it’s surprising that cross-species cloning has been tried, let alone had any successes. But it has. For example, two African wildcat kitten clones have been born from domestic cats, and three gray wolf clones have been born from domestic dogs. Again, though, the failure rates have been high.

And on the title’s subject of re-creating an extinct species:

Cloning a mammoth would be even more difficult. For one thing, elephants and mammoths are less closely related to each other than cats and wildcats or dogs and wolves, so the difficulties would likely be greater in any case. And elephants have a 22-month pregnancy — so you’d have to wait a long time to find out whether the experiment had worked.

Not only that:

But there’s a far more profound problem, as well. …. Because mammoth carcasses have been lying around for 10,000 years or more, their cells aren’t in good shape and their genomes are shattered. Instead of being neatly arranged in chromosomes, as ours are, mammoth genomes are in tiny pieces. So before we could put a mammoth genome into an egg, we would have to build one — something we are nowhere close to being able to do. Woolly mammoths will not be coming soon to a zoo near you.

All the same, research in this direction would surely yield astonishing discoveries. Our efforts to clone have opened up immense vistas of new research questions, and advances in the field have already shed light on fundamental aspects of how an embryo grows. During growth, cells become committed to being one type of tissue or another — heart muscle, say, or skin cells. Through cloning, we are learning how to reverse those commitments, something that may, one day, lead to revolutionary medical treatments. Likewise, learning to build a genome, whether of a mammoth or anything else, will certainly be interesting, and will probably be important in ways that we can’t foresee.

We’re convinced. And when cloning is perfected, we want our very own copy of Olivia.